The present invention relates to a decoding apparatus for decoding encoded video and audio data, and particularly relates to copyright protection technology.
The amount of information in digitized video and audio data is usually reduced by high-efficiency coding process and then the resultant data is multiplexed so as to be recorded on a recording medium or transmitted. The major examples of the recording medium include a DVD (Digital Versatile Disc). The major examples of the transmission include distribution via digital television broadcast or the Internet.
Video data is encoded mainly according to the MPEG-2 (Moving Picture Experts Group-2) standard, the MPEG-4 standard, or the like, while audio data is encoded mainly in accordance with Dolby Digital, DTS (Digital Theater Systems), MPEG Audio, PCM (Pulse Code Modulation), or the like.
Audio data encoded according to these encoding methods will be hereinafter referred to as “encoded audio data”. In many cases, multiple channels of audio data are encoded as encoded audio data.
If video and audio are converted into digital data, they can be recorded or transmitted more conveniently, while replication thereof without degradation becomes possible, leading to the problem of copyright infringement. In order to deal with this problem, a technique for embedding copyright information in video and audio data has been developed. Although detailed explanation of this technique will be omitted herein, this kind of technique has already been employed in DVD-Audio and the like, for example.
In the future, multiple types of copyright protection techniques may be employed according to the characteristics of contents. In that case, when a medium on which a plurality of contents can be recorded is played back, it is necessary to detect multiple types of copyright information.
For example, the pamphlet of International Publication No. WO2002/065783 discloses a technique for detecting two kinds of copyright information for images.
The disclosed technique, however, achieves commonality of processing by taking advantage of the fact that these two types of copyright information are both for images. Techniques to be developed in the future will not necessarily have commonalities with the prior technique. Therefore, detection of multiple types of copyright information may require simultaneous operation of a plurality of copyright information detectors, which may cause an increase in the amount of computation necessary for the detection.